I know there are lots of advanced technologies being developed for treating disease, but the same technologies could be used for non-disease applications. I wrote a little about this a few years ago. So I want to propose something that I think a lot of people would like:

Extra bladders

There are people working on 3d printed organs. Wouldn't it be cool to get a 3d printed bladder? Would you like to super-size that?

Even better, wouldn't it be cool if your supplemental bladder automatically ran tests on your urine, like these Japanese toilets do? The toilets developed in 2004 can measure glucose levels but I'm sure there are other tests that will be practical too. Plus, if it's done in your 3d printed bladder, it can be transmitted to your smartphone in real time over low energy bluetooth, like a Fitbit.